package middleware

import (
	"net/http"
	"sync"
	"time"

	"github.com/gin-gonic/gin"
)

type rateWindow struct {
	start time.Time
	count int
}

var rateWindows sync.Map
var rateMu sync.Mutex

// RateLimitByIP applies a fixed-window limit to public endpoints.
// A shared gateway limiter is still needed when running multiple replicas.
func RateLimitByIP(max int, window time.Duration) gin.HandlerFunc {
	if max < 1 {
		max = 1
	}
	if window <= 0 {
		window = time.Minute
	}
	return func(c *gin.Context) {
		key := c.Request.Method + ":" + c.FullPath() + ":" + c.ClientIP()
		now := time.Now()
		rateMu.Lock()
		allowed := false
		var current rateWindow
		if raw, ok := rateWindows.Load(key); ok {
			current, _ = raw.(rateWindow)
		}
		if current.start.IsZero() || now.Sub(current.start) >= window {
			current = rateWindow{start: now, count: 1}
			allowed = true
		} else if current.count < max {
			current.count++
			allowed = true
		}
		rateWindows.Store(key, current)
		rateMu.Unlock()
		if !allowed {
			c.Header("Retry-After", "60")
			c.AbortWithStatusJSON(http.StatusTooManyRequests, gin.H{"code": 429, "message": "请求过于频繁，请稍后重试"})
			return
		}
		c.Next()
	}
}